Lewis Hamilton testing the Mercedes F1 W04 in Jerez on the final day of the 2013 season's first test. Photograph: Sutton Images/Corbis

Ross Brawn has welcomed Lewis Hamilton's criticism of Mercedes's new car as the first testing session of the Formula One season came to an end in Jerez.

Hamilton said the new WO4 did not have the downforce to match his old McLaren drive after his first outing in Spain and after his second run on Friday he repeated that there was a great deal of work to be done

Brawn, the team principal, responded: "I think we have made it very clear to Lewis that he is part of the solution. You have a choice in a team, are you the problem or are you the solution?

"He is part of the solution to get us where we want to be. He knows that and he understands that and I think he is relishing that.

"It is correct that he gives his reference points and helps us understand what we have to focus on. Some of it we knew already and that is why we restructured the aero group. I welcome that approach. It needs to positive and constructive but criticism of the right sort is helpful to a team, it drives you forward."

Brawn added that he was delighted with Hamilton's direct approach. "He is very straightforward. In many ways he is very simple and straightforward. He tells us what he thinks and he is never short of detail in telling you what he thinks and, of course, you learn what level of detail you need to go to.

"He is interested in everything about the car. He is interested in the fact the stickers might not be put properly on the bodywork. He has got a very good eye for detail. I think he is going to be a very involved member of the team, which is what we wanted.

"He is clearly a very talented driver but Formula One is about so much more. There are a lot of highly talented drivers who don't have the rest of it, but I think he has got the rest of it as well."

But Brawn said: "The first couple of days were difficult with the problems we had. But since then it has been as good as I could have hoped. Today was Lewis's first proper day. It took a few runs to settle in but once we got past that it has been very constructive. "

Hamilton said: "We definitely need to work and understand the car more. There's a huge amount of work I need to do to fully understand everything. I need to do a lot of studying to understand the car before the start of the season. I've only done 59 laps but every one I do I learn a little more, but its going to take some time."